BALL JOINT

Provided is a ball joint in which a dust cover is fixed to a socket by a retaining ring and which has an improved waterproofing performance at a fitting region where the dust cover is fitted onto the socket. A ball joint 100 has a dust cover 140 fitted onto the outer periphery of a socket 120 formed into the shape of a cylinder with a bottom. The socket 120 has a dust cover groove 125 into which a socket fitting portion 141 of the dust cover 140 is fitted, and a dust cover receiving surface 126 for supporting a socket facing surface 143 of the dust cover 140. The dust cover receiving surface 126 inclines toward the socket facing surface 143 while extending from the outer side toward the inner side. Radial projections 142 are formed on the inner peripheral surface of the socket fitting portion 141 of the dust cover 140. Also, an axial projection 145 projecting toward the dust cover receiving surface 126 is formed on the socket facing surface 143 of the dust cover 140.